This invention relates to a gearshift device for a system for transmission of power in a motor vehicle, and a method of controlling the same.
Among various types of gearshift devices for an automated speed changing mechanism or automatic transmission (gearbox) provided in a vehicle, those which adopt so-called “Shift By Wire” scheme have been attracting attention in recent years as carrying advantages in downsizing of the device and reduction in the force required for operation thereof. JP 2002-254942 A (see Paragraphs 0020-0029, FIG. 2) and JP2003-327002 (see Paragraphs 0013-0017, FIG. 2) disclose exemplary implementations of such “Shift By Wire” type gearshift devices. The gearshift device adopting the “Shift By Wire” scheme is, in general, configured to switch gears in the automatic transmission using an actuator, based upon the position of a shift lever detected using a sensor or the like; that is, the gears of the automatic transmission are changed under electronic control. This configuration enhances the flexibility in design which determines the manner of manipulation of the shift lever. For example, the “momentary” actuation of a gear can be realized such that the shift lever, once placed in a specific gear and then released, is automatically returned to a home position.
Typically, the automatic transmission allows options of gear ranges: neutral, drive, reverse and low. Note that “parking” range, which could be deemed to be an option, is directed to lock the automatic transmission, and thus distinct from the aforementioned options of the gear ranges. The shift positions of the shift lever are indicated as “neutral”, “drive”, “reverse” and “low” in positions corresponding to these gear ranges. In the gearshift devices adopting the “Shift By Wire” scheme, the aforementioned “momentary” actuation can be enabled for every shift position, which keeps the shift lever in a predetermined (home) position at all times but when the shift lever is being manipulated, to ensure increased ease of gearshift operation.
On the other hand, however, keeping the shift position in a predetermined position would disadvantageously deprive the driver of a clue for recognizing which range is the current state of the automatic transmission. This could be most serious in situations which require frequent changes in shift position, such as: those which require repeated forward and backward operations of the vehicle as you may encounter in parallel parking, and those which require changes between low and drive ranges during driving the vehicle as you may encounter in taking a road through the hills. It has been previously proposed to provide a light-emitting indicator on the instrument panel or the like, to indicate symbols representative of the range of gears currently actuated, (for example, “R” for reverse gear range, and “L” for low gear range). The problem associated with this indicator, however, is that the driver is obliged to take his/her eyes off the outside of the vehicle to check up on the indication on the instrument panel.
To address the problem, assuming for example that the “momentary” actuation is disabled for the reverse and low positions with the shift lever kept in these shift positions without returning to the home position, the driver can recognize at least the low or reverse range as the currently actuated gear range by the position of the hand that grips the shift lever, so that the driver can swiftly make a decision as to manipulation of the shift lever in parallel parking of the vehicle or driving through the hills. Accordingly, by providing the shift lever with a retention property for the reverse and low positions while providing the same shift lever with a momentary actuation property for the positions frequently used during normal operations such as the drive position for normal driving operation and the neutral position used when the vehicle is to be at a stop, an excellent gearshift device with gearshift operation facilitated considerably can be realized.
However, if the shift lever is provided with such a retention property as described above, inconsistencies may take place such that when the driver gets off the vehicle, the status of the transmission is switched to the parking range though the shift lever remains in the reverse position. In this instance, on the next occasion when the driver gets on the vehicle, the driver is undesirably obliged to manually move the shift lever back to the home position before anything else.
The present invention has been made in an attempt to eliminate the aforementioned disadvantages, and it is one aspect of the present invention to provide a gearshift device and a method of controlling the same, which can achieve an improved gearshift operation in view of the problems discussed above.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.